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Adding 9, 19 and 99 Mental Maths Worksheet

Mental maths lesson 4: Add and take away 9, 19 and 99 · Set 156 · 40 questions
TalentJR

How to do it in your head (Round and adjust): Add 9, 19, 99: add 10, 20, 100, then take 1 away. Take away 9, 19, 99: take away 10, 20, 100, then add 1 back. Ask yourself: did I use too much or too little?

NameDateTime takenScore ___ / 40
  1. 1.13 − 9 =
  2. 2.36 − 29 =
  3. 3.191 − 99 =
  4. 4.52 − 19 =
  5. 5.47 + 29 =
  6. 6.26 + 29 =
  7. 7.202 + 99 =
  8. 8.74 + 9 =
  9. 9.16 − 9 =
  10. 10.39 − 19 =
  11. 11.55 + 29 =
  12. 12.35 + 9 =
  13. 13.62 + 19 =
  14. 14.108 + 99 =
  15. 15.45 − 29 =
  16. 16.88 − 19 =
  17. 17.59 + 19 =
  18. 18.705 + 99 =
  19. 19.23 − 9 =
  20. 20.587 + 99 =
  21. 21.29 − 9 =
  22. 22.64 + 19 =
  23. 23.82 − 19 =
  24. 24.49 + 9 =
  25. 25.164 + 99 =
  26. 26.33 + 19 =
  27. 27.67 − 9 =
  28. 28.484 + 99 =
  29. 29.85 − 9 =
  30. 30.92 − 19 =
  31. 31.30 + 29 =
  32. 32.768 + 99 =
  33. 33.17 + 9 =
  34. 34.46 + 29 =
  35. 35.19 + 19 =
  36. 36.81 − 29 =
  37. 37.740 − 99 =
  38. 38.34 + 29 =
  39. 39.76 + 19 =
  40. 40.53 + 9 =

Answer key

  1. 4
  2. 7
  3. 92
  4. 33
  5. 76
  6. 55
  7. 301
  8. 83
  9. 7
  10. 20
  11. 84
  12. 44
  13. 81
  14. 207
  15. 16
  16. 69
  17. 78
  18. 804
  19. 14
  20. 686
  21. 20
  22. 83
  23. 63
  24. 58
  25. 263
  26. 52
  27. 58
  28. 583
  29. 76
  30. 73
  31. 59
  32. 867
  33. 26
  34. 75
  35. 38
  36. 52
  37. 641
  38. 63
  39. 95
  40. 62

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